Seoul’s mid-May overnight minima typically span 12–16 °C under normal spring conditions, placing the market’s leading outcomes of 13 °C, 14 °C, and 15 °C squarely in the climatological sweet spot. A transitional La Niña phase over the western Pacific is currently favoring slightly cooler nighttime radiative cooling across the Korean Peninsula, nudging trader consensus toward the lower half of that range. Day-to-day variability arises mainly from differences in cloud cover, surface wind, and the strength of the nocturnal temperature inversion, which can shift the recorded minimum by 1–2 °C. Short-range guidance from the Korea Meteorological Administration through May 18 will determine whether the final low settles near the 13–14 °C cluster or edges higher under clearer, calmer conditions.